A standard coupling as described in application Ser. No. 10/387,124 filed 12 Mar. 2003 (now US Pat. No. 6,846,241) has an inner ring centered on an axis, an outer ring surrounding and generally coaxial with the inner ring, and an intermediate ring generally coaxial with and between the inner ring and outer ring. A pair of mainly angularly extending, flexible, and parallel inner links have inner ends attached at respective locations to an outer periphery of the inner ring and outer ends attached at respective locations to an inner periphery of the intermediate ring, and a pair of mainly angularly extending, flexible, and parallel outer links have inner ends attached at respective locations to an outer periphery of the intermediate ring and outer ends attached at respective locations to an inner periphery of the outer ring. The outer links extend transversely of the inner links, and the rings and links are unitarily formed with one another.
Thus with this arrangement there are two basic systems that compensate for misalignments of the driving and driven parts which are attached to the inner and outer rings. Deflections perpendicular to the inner links are compensated for by their deformation, and deflections perpendicular to the outer links are compensated for by their deformation. Deflections diagonal to the links are compensated for by deformations of all of them. The provision of the intermediate ring ensures complete noninterference between the inner and outer links while allowing the coupling disk according to the invention to transmit considerable torque.
Another known type marketed as a type K Centaflex coupling has a plastic body in which there is a central metallic hub surrounded by an annular array of cast-in-place metal sleeves. Another prior-art such assembly is described in Kupplunasatlas (A. Schalitz; A. G. T. Verlag Georg Thum; 4th edition 1975.) Bolts extending through the sleeves secure the coupling to a flywheel or the like and a shaft is fitted to the hub. A complex screw clamp is provided to hold the metallic hub in place. Such a coupling is expensive to produce. In addition it is delivered to the user as several pieces that must be assembled on the site.